The present application claims Convention priority from Japanese Patent Application No. 2013-72388 filed on Mar. 29, 2013, the full content of which incorporated herein by reference.
In a pupil plane of an optical system of an imaging camera, the technique called “Wavefront Coding,” hereinafter referred to as “WFC,” for extending a depth of field and/or a focal depth of an optical system. The WFC uniforms blur of a point for defocus by providing a phase distribution given by a cubic function to a coordinate on the pupil plane and removing the uniformed blur by an image processing called deconvolution.
As the related art regarding the WFC, the technique is proposed such that a focal depth of an optical system is extended by processing a captured image with phase modulation of a pupil function with a phase filter realized by implementing a cubic phase function in an optical system of an imaging camera, for example. See PTL1. Further, the technique for extending a focal depth such that, when employing a x-y coordinate orthogonal to an optical axis as a phase filter for modulating an optical transfer function, hereinafter “OTF”, a captured image is processed by providing a phase distribution obtained by normalizing a cubic function with a series of the function represented by a product of arbitrary power of the same. See PTL2. Furthermore, although not for an imaging optical system, the technique for attempting improvement in efficiency in wave length conversion for laser by generating a non-diffraction beam using a conical prism called “axicon” is also proposed. See PTL3.